Tail gate for loading and unloading vehicles



Jan. 20, 1953 R. F. w. BERFORD ETAL 2,

TAIL GATE FOR LOADING AND UNLOADING VEHICLES Filed Aug. 8, 1949 6 Sheets-Sheet l mm NM mm mm IIVl EM'DPS ROM/P7- Frw sa iak'a, az/vrozv W W000,

BY MW Jan. 20, 1953 R. F. w. BERFORD ETAL 2,525,067

TAIL GATE FOR LOADING AND UNLOADING VEHICLES Filed Aug. 8, 1949 6 Shee'ts-Sheec. 2

s 5 l6], 5 m 'm 5 g 5 J Q FJ I Ft I y H 1751717. .51 L7 LL'FJIAYJZZZMZID BY/MWME Jan. 20, 1953 R. F. w. BERFORD EFAL 2,626,057

TAIL GATE FOR LOADING AND UNLOADING VEHICLES Filed Aug. 8, 1949 6 Sheets-Sheet 5 Jan. 20, 1953 R. F. w. BERFORD EIAL 2,626,067

TAIL GATE FOR LOADING AND UNLOADING VEHICLES Filed Aug. 8, 1949 6 She ef cs-Sheet 4 Jan. 20, 1953 RF. w. BERFORD ETAL TAIL. GATE FOR LOADING AND UNLOADING VEHICLES 6 Sheets-Sheet 5 Filed Aug. 8, 1949 4 I6 CL/NfOIV 4 W000 Arum ms Jan. 20, 1953 R. F. w. BERFORD EIAL 2,625,067

TAIL GATE FOR LOADING AND UNLOADING VEHICLES Filed Aug. 8, 1949 6 Sheets-Sheet 6 Patented Jan. 2 0, 1953 TAIL GATE FOR LOADING AND UNLOADING VEHICLES Robert Fitz WV. Berford, Dearborn, and Clinton W. Wood, Grosse Point Farms, Mich., assignors to Phil Wood Industries Limited, Windsor, ntario, Canada, a company of Canada Application August 8, 1949, Serial No. 109,215

19 Claims.

This invention relates to apparatus, commonly knownas a tailgate loader, for loading and unloading vehicles.

In apparatus of this type a platform connected to the vehicle and adapted to receive a load at ground level is raised to the height of the floor of the vehicle, while maintained substantially horizontal, and then after the load has been moved onto the vehicle, is pivoted, either manually or by power operated means, into a vertical position to form the tailgate of the vehicle. Such tailgate loaders have come into wide use because they make it possible for one man to load a vehicle with heavy crates, drums and the like at points which are not provided with fixed loading platforms level with the floor of the vehicle. The known tailgate loaders are subject to a number of disadvantages however, among the most importantof, which are the following:

Most ofthe known devices involve the use of parallel arms or links inv order to hold the platform parallel to the ground as it is raised and lowered and this structure is likely to be damaged if the vehicle is unloaded with its wheels on a surface above the surface to, which the tailgate will be lowered. When the platform drops below the level of thewheels, the links cross and bend orabreak;

A further disadvantage is thefact that since the known platforms are held substantially parallel to the ground throughout the raising and lowering by the parallel links and since the link "connections at the rear edge of the platform projectdown from the bottom of the platform so as to hold that edgeup from the ground, the outer or frontedge of the platform should be provided with blocks to support it at ground level, and a small ramp should be provided which will enable heavy articles to be rolled onto the platform.

An important disadvanta e of-the known tail,- gate loaders provided with two different control levers, one for raising and lowering the plat.- form and theother for pivoting it to thevertical position, is that there is a real danger of the wrong lever being; used to stop the platform, so that it will be pivoted and the load thrown off and, damaged. There is also a danger of the wrong lever being used while the platform is being raised or, lowered. I

Another disadvantage of most of the known tailgate loaders is. that the hydraulic cylinders are directly connected to the parallel arms for raising of the platform so that all of the weight 'ofthe tailgate loader'is concentrated at the rear of the vehicle and it is frequently necessary to cut away parts of the vehicle chassis in order to provide for the hydraulic cylinder assembly and movement of its piston.

Th objects of the present invention are to provide a tailgate loader which avoids all of: the abovementioned and other disadvantages. The novel structure. replaces the parallel arms with a cam and roller arrangement which not only makes it possible safely to lower the platform below the level of the ground on which the ve-.- hicle is resting but makes it possible by. appropriate shaping of the cam contour to allow the outer edge of the platform to drop down onto the ground after the inner end with its projection has reached the ground so that the outer end may be provided with a knife edge permitting small hand trucks and drums to be rolledonto the platform Without difficulty. The lifting arms connected to the platform are operated by a torque member which is rotated by means which permit the hydraulic cylinder assembly to be placed ahead of the rear vehicle axle while the balance of the tailgate is at the rear of the axle in the usual way, there. being avoided in this way the necessity for cutting away part of the vehicle frame or in any way interfering with it. The pivoting of the platform to the vertical position is effected through a second hydraulic cylinder assembly and the two assemblies areinterconnected in a novel manner through a valve means controlled by a single lever in such manner that. the fluid under high pressure required to operate the second assembly to pivot the platform is obtained from the first assembly, and is so obtained only when the platform is level with the. vehicle floor, and only after further movement of the hand lever.

The above, and other objects and features of th invention will appear from the following description with reference to the drawings, in which Figs. 1A and. 1B, form aside view of the apparratusaccording to the invention as applied to the vehicle shown in dotted outline,

Figs. 2A and 213 form a plan-view-correspondp ing to the greater part of Fig. 1,

Fig, 3 is a rear elevation of the apparatus: illustrated in Figures 1 and 2;

Figures 4, 4A and 4B are kinematic-line diagrams illustrating respectively the positions; of the elements when the platform has been swung into the closed tailgate position when theplatform is at the level of the vehicle floor, andwhen the platform is resting on the ground}.

Fig. is an enlarged detail of the quadrant with the chain connected,

Fig. 6 is a diagram showing the position of the operating hydraulic pistons and their control valve when-the valve has been moved to the position to raise the tailgate,

Fig. '7 is a diagram illustrating the position of the control valve when the tailgate is held stationary in a partly raised position.

Fig. 8 is a diagram illustrating the position of the control valve for pivoting of the tailgate into the vertical position, and

Fig. 9 is a diagram illustrating the position of the control valve when the tailgate is being lowered to the ground. I

In order that the construction might be illustrated on the largest scale possible, the elevation and plan views of Figures 1 and 2 have each been divided between two portions, the left hand portion in each case being designated A and the right hand'portion B. The tailgate loader may be considered as comprising two groups of parts, first the tailgate itself, with its supporting and raising arms and levers, as shown in Figure 1B, and second the hydraulic system, illustrated in Figures 6-9, for actuating the tailgate.

Asshown in Figures 1B, 2B and 3, a flanged plate In is secured to each side sill of the vehicle frame near the rear end thereof so as to project downwardly therefrom. At the lower end of each plate In there is rigidly mounted a bearing I2 (Figures 2B and 3), and in the two bearings thus provided there is journalled a torque member which is conveniently a tube I 3. Each bearing I2 carries-a cam plate I4 (Figures 1B, 3, 4A and 4B) rigidly secured to the bearing for the purpose described below.

The torque tube I3 has rigidly secured thereto :at each end, so as to be swung through an are on rotation of the tube I3, a lifting arm I 5 proconnected at the end opposite the torque tube I3 to the underside of the tailgate I6 by pins IT, as illustrated in Figure 13. Referring particularly to Figures 23 and 3 a shaft I8 is journalled in bearings I9 mounted one in each of the arms I5 midway between its ends. Adjacent each bearing I9, and aligned with a cam plate I4, there is mounted on shaft I8 a pair of levers 20 secured to hubs 2| keyed by pins 22 to shaft I 8. 4 As appears from Figure 113, one end of each pair of levers 20 is connected to a link 23 by a pin passing through the pair of levers and throughthe link 23, the other end of the link being pivotally connected to the tailgate by pins 25 at a point which is above pins I I and is closer to the torque tube I3, when the tailgate is in the horizontal position illustrated in Figure 113, than are the pins I1.

A roller 23 is mounted for rotation between the levers 20 of each pair at the end thereof opposite links 23 and the roller is adapted to cooperate with and travel over cam plate I 4, which is aligned therewith, as appears from Figures 1B 'to cause its outer end to pivot downwardly about the pins I1, thus urging the levers 2!! to pivot counterclockwise, as seen in Figure 1B. Thus the weight of the tailgate forces the rollers 26 into contact with the cam plates I4, and the cam plates serve to limit and regulate the pivoting of the levers 20 under the influence of the weight of the platform.

The torque tube I3 is caused to rotate, in order to lift the arms I5, by the chain and quadrant arrangement illustrated in Figure 5. The quadrant 21 is rigidly secured to the torque tube I3 so as to rotate with it, and it is provided with a tail portion 28 rigidly secured to a bearing 29 carried on shaft I8 for the purpose of supporting and strengthening shaft I8, which is subjected, when the tailgate carries a heavy load, to stresses tending to cause the shaft I8 to bow upwardly. The quadrant 21, which acts as a crank member, is provided at each side with an arcuate plate 30 so that the two plates 30 define between them a groove 3| of a width to receive every second link of a chain 32 connected to the quadrant by a clevis 33 and pin 34. As appears from Figures 1A and 2A, the chain 32 is connected at the other end by a clevis 35 and pin 36 to an adapter member 31 connected to the piston rod 38 of the main hydraulic cylinder 39, which is supported on braces 40 and 4|, supported on the sills II of the vehicle frame. As illustrated, the adapter 31 is formed so that it may be engaged by a hook 42 pivotally mounted between lugs 43 mounted on the end of the cylinder 39, the purpose of the hook being described below.

As mentioned above, the weight of the tailgate in the horizontal position urges the rollers 26 into contact with the cam plates I4. In order to pivot the tailgate on the pins I1 into the vertical closed position illustrated in Figure 4, the shaft I8 is rotated in a clockwise direction as viewed in Figure 13, with the effect of raising the rollers 26 from the cam plates I4 and drawing the links 23 downwardly as illustrated in Figure 4.

Shaft I8 is rotated in this way by hydraulic cylinder 44, the piston rod 45 of which is connected to a crank lever 46, preferably formed as an integral part of hub 41 which is suitably keyed to shaft I8. Referring to Figures 23, 4 and 4A, it will be seen that as the piston rod 45 is drawn into the cylinder 44, the crank lever 46 is pulled upwardly, causing the shaft I8 to rotate clockwise. Cylinder 44 is pivotally mounted between lugs 48 formed on torque tube I3, so that it may pivot to the extent required by relative rotation of tube I3 and shaft I8 as arms I5 are raised.

Comparing Figures 4, 4A and 43 it will be seen that in Figures 4 and 4A the piston rod 38, quadrant 21 and lifting arms I5 are in the same position since the elevation of the platform has not changed but since Figure 4 shows the platform swung into the vertical closed tailgate position, the piston rod 45which is extended in Figure 4A has been retracted in Figure 4 whereby the shaft I8 has been rotated as noted above, and the rollers 23 have been raised from the cam plates I4. In Figure 4B the piston rod 45 is in the same extended position as in Figure 4A, the cylinder 44 having been merely pivoted on lugs 48 due to the change in position of shaft I8 as the lifting arms are lowered and the shaft I8 describes an are about the torque tube I3. However the piston rod 38 in Figure 4B is not in the same position as in Figures 4 and 4A but is extended.

Fluid under pressure is provided for the cylinders 39 and 44 by a pump 49 (Figure 1A) driven by shaft 50 from a power take-off 5i controlled by: lever 52'. Fluid is .fed from the; pump; :49. to control valve ii boltedto the pump 49 aszshown in Figure IA andillustrated in section. in Figures 6-9; The control valve 53 is provided. with abore 54" and apiston or spool 55 adapted to-reciprocate therein in accordance with. the rocking movements of :a bell crank. 56., one arm of which is connected to the spool 55 by a link 51. The other arm of crank 5.6v is connected-to .a rod 58. (Figures 1A and 2A) connected to one end of a lever 59 pivoted at Won the brace 40. The other end of the lever 59 is connected. to rod 6| which extends to the rear of the vehicle and is connected to the free. end of a lever arm 62. (Figure. 1B.) mounted on a. cross. shaft 63 provided with a handle. as best. illustrated. in Figure 2B. On movement. of. the handle 64 to the appropriate position. illustrated. in Figure 1B the. rods 61 and are reciprocatedtoadjust the'spool 5.5 of the spool valve53 in bore 54.

The lever 59 is provided between its pivot point 60 and its connection to rod 6| with an arm 5.5,. which is adapted, at theextremes of a range of movement of the lever 59 under the infiuence-of the rod 61, to pivot the hook 42. The hook .42 is provided with an integral pivot pin 66 which has rigidly connected to one end thereof aalever arm 6"! to'the f-reeend of whichis pivoted a rod 6-8 threadedv at the end opposite the lever arm- 61 and provided with a spaced pair of locked nuts 69- and I0. Freely movable on the rod 68, betweenthe nuts 69 and I6 is a block H pivotally mounted on arm 65 so that as the arm 59, is pivoted the block H moves between the nuts 69 and 10.. When the handle 64 is moved to the lower position indicated in Figure 1B, the arm .59 is pivoted counterclockwiseas seen in Figure: 1A, until the nut 69 is engaged by the ensure that the hook 42 has-dropped into the re- -cess provided in the hook 31.

If the hook has merely dropped on to the piston rod, the nut l will. prevent pivoting of thearm 59 far enough to permitsuflieientmovement of .therod 58 to move spool- 55 to. the position required to operate the hydraulic system to pivotthe tailgate, into the closed position. It. is, therefore, impossible to pivot thev tailgate into the vertical closed position .until the tailgate. has reached the levelof the vehiclefloor and the. hook 42 has engaged the .adapter 31.

Referring now toFigures 69, the control valve =53 =isiprovided withan inletport i2 for fluid under high pressure from the pump 49 and. with outlet; -ports- 13. and 14.-connected to the .low pres.- sure side of the pump, and two connections to each of the hydraulic cylinders 391and44. When the spool 55-is in the position illustrated in Figure 6, high pressure fluid from inlet 12 travels .tl-irough. passage .75 to bore 54 and since lands 16 and. H formed on the spool 55 prevent the fluid f-romireaching any other passages, the fluid passes through passage l8 to fluid line 19 tocylinder 39 behind piston 80 thereby forcing the piston 66 andgits-rod 36: to. the-right as seen in Figures 6-9., 'whereby'the torque tube 1.3 is. rotated by chain and quadrant 21' to raise the tailgate l6. Oil is-thus torced from the cylinder ahead ofthe-piston through the. ports 81. and, 82,. the-.former leading through line 83' to passage 84 in com-'- munication with the portion of bore 54 above land H, .and port 82 leading to the same portion to bore 54 through lines 85 and 86. This portion of bore 54 is in communication with outlet 73 through passage 81, and outlets l3 and .14 are joined by passage 88.

When handle 64 has been moved to the raise position. indicated in Figure 1B the spool 54 is positioned as illustrated in Figure 6 and so long asthehandle 64 is left in that position thepiston 66' moves to the right until piston 80 moves beyondport 81. as illustrated in Figure 8, whereupon fluid. under high pressure escapes to outlets l3 and 14 through port Bl. On this escape. of fluid through port 8!, the fluid pressure acting on piston 66 drops so that the piston 86 is not moved furthertoward the right. The weight of the tailgate and any load it may be carrying urges the piston 86 to the left to a position which would close the port. 85., and thereby allow the pressure. to the left of the. piston to build up again. Thus the fluid pressure acting on the piston 80 is automatically balancedv against the weight .of the tailgate and its load as soon as the piston 66 has moved to the position. illustrated inFigure 8.. Extreme movement of the piston 86 to the right is prevented by a piston rod extension ta-engaging. the end wall 96 of the cylinder 39.

It may be desired to hold the. tailgate .at .a certain level below the vehicle floor but above ground level, and in that case the handle 64 is moved. to the hold position, which moves the spool 55. to the position indicated in Figure 7 in which land ll blocks passage 18. so that fluid under high pressure can not pass to fluid line '59 and the fluid in cylinder 69 tothe left of cylinder 86 can not escape so as to allow piston 6-6 to move to the left.

When the handle 64 is in the raisewposition so that the piston 86 is moved to the position illustrated in Figure 8, the pair of nuts 69 (Figure 1A) is not engaged by the arm 65 so that the hook 42 drops on to the extended piston rod 38. As the. piston 8i! reaches the position illustrated in Figure 8 the hookdrops intothe recess provided in the adapter 3'5 as mentioned above and thereby the pair of nuts. 30 is moved clear of the position which the arm 65 must occupy when the handle .64; .is .moved to the extreme position required for pivoting the tailgate into the upright position. When the load has been moved-on to the vehicle and the. handle 64 has been moved to this pivot position, the spool 55 ispositioned as illustrated in Figure 8. with land 26 blocking bore 54 below passage. 15 andland ll blocking passage 84 atits entrance "to bore 54. Fluid under high pressure is thus forced through line i9, cylinder 35, line 83 and passage 64 to. line 92, which leads to cyl- .inder 44 behind. its piston 63. Piston t3 and rod 45. are thus moved to the right so that, referring to Figures 4 and 4A,. rod 45 is withdrawn into cylinder 44 and lever 46 rotates shaft I8 in a clockwise direction, thereby lifting rollers '26 from cam plates l4 as seen in Figure 4, so that the tailgate is pivoted on the pins ll. When the tail.- gate I6 has reached a position which is within about 20 of the vertical, its own weight and balancing. will bring it into the vertical position without further action by piston rod 45 and lever 46. Accordingly ports 94 and 95 which lead to line 96 (and thus/to. exhaust through line 8-6, bore 54 above land H and passage 8?) are so positioned as-to allow the fluidunder high pres" to port 14.

sure behind piston 93 to escape to exhaust after the tailgate has passed the balance point. Thus it is not powered during the last part of its movement, in which a mans arm might be caught between the tailgate and the vehicle side racks. While an arm so caught would be damaged by a tailgate closed under its own weight, the injury would be very much less severe than if the tailgate were powered at the time.

The use of the auxiliary chamber 91 makes it unnecessary to provide two exhaust lines from cylinder 44. Before ports 94 and 95 are reached by piston 93 fluid ahead of piston 93 passes through them and through port 98 into chamber 91 and thereafter, until ports 94 and 95 are uncovered, the fluid ahead of piston 93 passes only through port 98.

When the tailgate is to be lowered and the handle is moved to the lower position indicated in Figure 1B, the lever 59 is moved counterclockwise as viewed in Figure 1A, so that arm 5 moves down rod 68 to engage nut 69 and lift hook 42 clear of the adapter 31. At the same time rod 58 is moved to position spool 55 as illustrated in Figure 9 in which land 11 prevents fluid under high pressure from port 12 reaching passage 18 and line 19 and clears passage 9| so that fluid under high pressure passes from port l2 through passage 15, bore 54, passage 9| and outlet 13. Because land 11 is below passage 18, fluid to the left of piston 89 in cylinder 39 is forced by the weight of the tailgate acting on piston rod 38 through line 79 to passage 18 and bore 54 and from there through passage 81 to outlets l3 and 19. At the same time lines 83, 85, 92 and 96 are all in communication with bore 54 above land TI and thus with passage 81 and outlets 13 and M. The tailgate thus drops under its own weight, its movement being controlled by the rate of passage of fluid from cylinder 39 to the left of piston 99. As the tailgate drops, the shaft [8 describes an are about the torque tube 19 and the tailgate gradually approaches and passes the balance point at which it pivots under its own weight into the horizontal position. The handle 64 is then moved to the raised position so that the tailgate is lifted level with the vehicle floor and unloading of the vehicle proceeds. Alternatively the tailgate may be pivoted to the horizontal position by hand.

Referring to Figures -6-9, it will be seen that the only case in which cylinder 44 is not in free communication with exhaust on both sides of piston 93 is Figure 8 when fluid under high pressure is forced from cylinder 39 to cylinder 94 through lines 93 and 92 to pivot the tailgate into vertical position. At all other times piston 93 is free to move in cylinder 44 as a result of relative rotation of torque tube [3 and shaft I8.

It is necessary, as a practical measure, to provide a relief valve adapted to release excess pressure in passage 78 and line 19 if too great a load has been placed on the tailgate and accordingly a relief valve 99 is placed in passage I00, which is in communication with passage 18 and line 19. Passage l9l leads from relief valve 99 It is also desirable to prevent the tailgate being pivoted to the closed vertical position before the load has been removed therefrom. Referring to Figure 8, it will be seen that too great a resistance to the movement of the piston 93 reacts on relief valve 99 through lines 92, 83 and 19 and it is adapted to release high pressure fiuid to port 14 accordingly. The single relief valve can thus be used to relieve the pres sure in the system if a weight over a figure, which will for example be taken as 2000 pounds, is placed on the tailgate and the handle is moved to the raised position, and also to relieve pressure if, when there is still a load of say pounds on the tailgate, the handle is moved to the position to pivot the tailgate to the closed vertical position.

What we claim as our invention is:

1. Apparatus for loading and unloading vehicles, comprising, a torque member, means for mounting the torque member on a vehicle for rotation, spaced arms rigidly secured to the torque member and extending outwardly of the vehicle, a loading platform pivotally connected to said arms, means for rotating the torque member, levers pivoted between their ends on an axis substantially parallel to but spaced from the torque member, links pivotally connected at. one to one end of said levers and at the other end to the platform at points which are above the points of connection of said arms to the platform and are closer than such points to the torque member, and means adapted to cooperate with the other end of said levers to maintain the platform substantially horizontal during raising and lowering thereof.

2. Apparatus for loading and unloading vehicles, comprising, a torque member, means for mounting the torque member on a vehicle for rotation, spaced arms rigidly secured to the torque member and extending outwardly of the vehicle, a loading platform pivotally connected to said arms, means for rotating the torque member, levers pivoted between their ends on an axis substantially parallel to but spaced from the torque member, links pivotally connected at one end to one end of said levers and at the other end to the platform at'points which are above the points of connection of said arms to the platform and are closer than such points to the torque member, rollers at the other end of said levers, and cam means adapted to cooperate with said rollers to maintain the platform substantially horizontal during raising and lowering thereof.

3. Apparatus for loading and unloading vehicles, comprising, a torque member, means for suspending the torque member from a vehicle for rotation about an axis extending across the length of the vehicle, spaced arms rigidly secured to the torque member and extending rearwardly of the vehicle, a loading platform pivotally connected near one edge thereof to said arms, means for rotating the torque member to raise the spaced arms and platform, levers pivoted between their ends on an axis substantially parallel to but spaced from the axis of rotation of the torque member, links pivotally connected at one end to one end of said levers and at the other end to the platform at points which are above the points of connection of said arms to the platform and are closer than such points to the torque member, rollers at the other end of said levers, and cam means adapted to cooperate with said rollers to maintain the platform substantially horizontal during raising and lowering thereof.

4. Apparatus for loading and unloading vehicles, comprising, a torque member, means for suspending the torque member from a vehicle for rotation, spaced arms rigidly secured to the torque member and extending outwardly of the vehicle, a loading platform pivotally connected near one edge thereof to said arms, means for rotating the torque member to raise said spaced arms and platform, a shaft journalled for rotation in said arms 7011 an axis substantially parallel to but spaced "from. the torque member, levers rigidly mounted between their ends on said shaft, links pivotally connected at one end to one end of, said. levers and at the other end to the platform at points which are above the points of connection of said arms to the-platform and are closer than such points tothe torque member, rollers at the other end "of said levers, and cam means adapted to cooperate with said rollers to maintain the platform substantially horizontal during raising and" lowering thereof.

'5. Apparatus for loading and unloading vehicl'es, comprising a toroue member, means for mounting the torque member on :a vehicle for rotation, spaced arms rigidly secured to the. torque member and extending outwardly ofthe vehiclaia loading'platform pivotally connected to saidarms, means for rotating the torque member, levers pivoted betweentheir ends on an axis substantially parallel 'tobut spaced'from the toroue member, links pivotally connected at one 'end -to one end of said levers and at the other end to the platform 'at points Whichare above 'the points of' -connection of said arms to the'platform and are closer than such :points to the torque member, rollers at the other end of said levers, cam means: adapted to cooperate with said rollers to maintain the platform substantially horizontal during raising and lowering thereof, andv means operabl'eto pivot said levers in a directionjto pivot the platform into a vertical position.

6. Apparatus for loading and unloading vehicles. compris ng. a toroue member, means for suspending the torque member from a vehicle for rotation, spaced'arms rigidly sec red to the toroue member'and extendin outwardly o the vehicle, aloa rling platform 'pivotallv connected near one edge thereof to said arms, means for rotating the tor e member to raise said spaced arms and platform, a shaft journalled for rotat on in said arms *on an ax s substantially parallel to but spaced from the axis of thetoroue member, levers rigidly mounted between their ends on said shaft, links pivotally connected at one end to one end of said levers and at the ot er end to t e plat orm at points which are above the-points of connection ofsaid arms'to the p atform and are closer than such points to the torque'member, roller means at the other end of said levers. cam means "ada ted to coo erate with said roller means to regulate pivot ng of said levers n relat on-t said arms underthe influence of the weight of the platform so as to maintain the platform-substantially horizontal during raising and lowering thereof, and means o erable, after theplatform has reached a level approximately equal to that o'f't'he-vhicle floor, to pivot said levers in'a directionto p'ivot'the-p'latform into a vertical osition.

'7. Apparatus for loading and unloading vehicles, comprising, a torque member, means for sus ending the toroue member at the rear of a vehicle for rotation about an axis extending across the length of the'vehicle, spaced arms 10: are above the points of connection of said arms to the-platform and are closer than such points to the torque member, roller means at theother end of said levers,"cam means adapted to cooperate with said roller means toregulate pivotingof said levers in relation to said arms under the influence of the Weight-of the platform so as to maintain the platform substantially horizontal during raising and lowering thereof, and :means operable, after the platform has reacheda level approximately equal to that of the vehicle floor, to pivot said levers in a direction to pivot the platform into a vertical position, said last mentioned means comprising a crank lever rigidly connected to said shaft, a hydraulic cylinder, a

piston movable therein and connected to said crank lever, and means for admitting fluid under pressure to said cylinder after the platform has reached said level.

8. Apparatus for loading and unloading vehicles,'-comprisin-g, a torque member. means for suspending the toreue member at the rear of a vehicle for rotation about an axis extending across the length of the vehicle. s aced arms rigidly secured to the torque member and extending rear ardly of the vehicle, a loading platform pivotally connected near oneedge thereof to said arms, a main hydraulic cylinder, apiston movable therein. crank means rigidly connected to the toroue member and connected to said piston for rotating the torouemember to=raisesaid spaced arms and platform. means for admitting fluid under pressure to said cylinder, a shaft journalled for rotation in said arms on an axis substantially p-arallelto but spaced from the axis of the torque member, levers rigidly'mounted between their ends on said'shaft, links pivotally connected at one end to one end of said-levers and at the other end to the platform at points which are above the points of connection of said arms to the platform and are'closer than such points to the torque member. roller means at the other end of said levers, cam'means ada ted to cooperate with said roller means to-maintain the platform substantially horizontal during raising and lowering thereof, and means'o'perable, after the platform has reacheda level approximately equal to that of the vehicle floor; to rotate said shaft to pivot said levers in a direction to ivot the latform into a'vertical position, said last mentioned means comprising a crank lever rigidly connected to said -shaft,.:a second hydraulic cylinder, a pistonmovable'therein and connected to saidzcrank lever, and means for diverting fluid under pressure from. said main cylinder to said second cylinder to act. on. the piston movable therein after the platform has reached said level. I I

9.. Apparatus as defined'in claim 8, inwhich said main cylinder is provided with an outlet adapted to be opened by the piston inovable therein when the platform reaches said level, and means is provided operable to pass the fluid un-- der pressure acting on said pistonffrom said outlet to'the second cylinder.

10. Apparatus as defined'in claim 9 in which said means for passing fluid to the second cylinder comprises a multi -way'valve, afiu-id line connecting the valve to theinlet of the main cylinder, a fluid line connecting said outletof the main cylinder to the; valve, :a fluid line connecting the valve to the inlet of the second cylinder, said valve having at least two operating positions in one'of which fluid under pressureis fed 'to the mlet. ofthe. main cylinder, and any fluid reaching the valve from the line connecting said outlet and the valve is passed to exhaust, whereas in a second operating position fluid under pressure is fed to the inlet of the main cylinder but fluid reaching the valve from said outlet is passed to the inlet of the second cylinder, and an operating lever adapted to place said valve in a selected one of said positions.

11 Apparatus asdefined in claim 10, comprising means adapted to prevent movement of said operating lever to place the valve in the second mentioned position until said outlet has been opened to the fluid acting on the piston movable in the main cylinder.

12 "In vehicle loading and unloading apparatus comprising, a loading platform, means for raising the platform from'ground level to the level of the vehicle floor and means for pivoting the platform into the vertical osition to serve as a tailgate; a main hydraulic clyinder, a piston movable therein and connected to actuate said means for raising the platform, a second hydraulic cylinder, a piston movable therein and connected to actuate said means for pivoting the platform into the vertical position, means for admitting fluid under pressure to said main cylinder to move its piston to raise the platform, means adapted, when the platform reaches a level approximately equal to that of the vehicle floor to divert fluid under pressure from the main cylinder auto matically to balance the fluid pressure acting on the piston thereof against the weight of the platform and its load acting on said piston, and means for passing said diverted fluid to said second hydraulie cylinderto pivot the platform into the vertical position. 7 a

13. In vehicle loading and unloading apparatus comprising, a loading platform, means for raising the platform from ground levelto the level of the vehicle floor and means for pivoting the platform into the vertical position to serve as a tailgate; a main hydraulic cylinder, a piston movable therein and connected to actuate said means for-raising the platform, a second hydraulic cylinder, a piston movable thereinand connected to actuate said means for pivoting the platform into the vertical position, means for admitting fluid under pressure to the main cylinder to move its piston to raise the platform, at least one port in said main cylinder adapted to be opened by the piston movable therein to -the fluid under pressure acting on said piston when the platform has reached a level approximately equal to that of the vehicle floor, and means for passing fluid from said port to exhaust or to said second cylinder .to pivot the platform into the vertical position. a

14. In vehicle loading and unloading apparatus comprising, a loading platform, means for raising the platform from ground level to the level of the vehicle floor and means for pivoting the platform into the vertical position to serve as a tailgate; a main hydraulic cylinder, a piston movable therein and connected to actuate said means for raising the platform, a second hydraulic cylinder, a piston movable therein and connected to actuate said means for pivoting the platform into the'vertical position, each of said cylinders having .an' inlet for fluid under pressure and, spaced therefrom, an outlet adapted to be opened by the .piston movable in such cylinder to the fluid under pressure acting on such piston, the outlet of the main cylinder being positioned so that it is opened when the platform has reached a level approximately equal to that of the vehicle floor, and

means operable to pass fluid under'pressure from said outlet to the inlet of the second cylinder.

after said outlet has been opened to the fluid act-- ing on the piston movable in the main cylinder;

15. In vehicle loading and unloading apparatus comprising, a loading platform, means for raising the platform from ground level to the level ofthe vehicle floor and means for pivoting the platform into the vertical position to serve as a tailgate; a main hydraulic cylinder, a piston movable therein and connected to actuate said means for raising the platform, a second hydraulic cylinder,- a piston movable therein and connected to actuate said means for pivoting the platform into the ver-' tical position, each of said cylinders having an inlet for fluid under pressure and, spaced therefrom; an outlet adapted to be opened by the pis-' ton movable in such cylinder to the fluid under pressure acting on such piston,'the outlet of the, main cylinder being positioned so that it is opened when the platform has reached a level approximately equal to that. of the vehicle floor, and the outlet of the second cylinder being positioned so that it is opened after the platform has passed its balance point but before it has reached the vertical position, and means operable to pass fluid under pressure from said outlet to the inlet of the second cylinder after said outlet has been opened to the fluid acting on the piston movable in the main cylinder. 1 1

16. Apparatus as defined in claim 15, in which said means operable'to pass fluid under pressure from said outlet of the main cylinder to the inlet of the second cylinder comprises, a multi-way valve, a fluid line connecting the valve to the inlet of the main hydraulic cylinder, a fluid line connecting said outlet to the valve, a fluid line connecting the valve to the inlet of the second hydraulic cylinder, said valve having at least two operating positions in one of which fluid under pressure is fed to the inlet of the main hydraulic cylinder, and. any fluid reaching the valve fro-m the"line connecting said outlet and the valve is passed to exhaust, whereas in a second operating position fluid under pressure is fed to the inlet of the main hydraulic cylinder but fluid reaching the valve from said outlet is passed to the inlet of the second hydraulic cylinder, and an operating lever adapted to place said valve in a selected one of said positions. a

' 17. Apparatus as defined in claim 16, comprising means adapted to prevent'movement of said operating lever to place the valve in the second mentioned position until said outlet has been opened to the fluid acting on the piston movable in the main hydraulic cylinder. 7 4

18, Apparatus as defined in claim 16, inwhich said multi-way valve is adapted in another operating position controlled by the same operating lever to open the line connecting the valve and the inlet of the main hydraulic cylinder to exhaust, and to permit fluid to enter the main cylinder on the side of its piston opposite its inlet, whereby the platform is allowed to settle to the ground under its own weight.

19. Apparatus as deflined in claim 18, in which saidmulti-way valve is adapted in still another operating position controlled by the same operating lever to close off the line between the valve and the main cylinder inlet against fluid flow in either direction whereby the platform is held stationary.

. ROBERT FITZ WM. BERFORD.

CLINTON W. WOOD.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,620,256 Heise Mar. 8, 1927 1,733,988 Barnard Oct, 29, 1929 Number 14 Name Date Novotney May 16, 1944 Day July 18, 1944 Penney Dec. 4, 1945 Wohlforth Dec. 21, 1948 Wood May 3, 1949 Reddngton Aug. 2, 1949 

